1. Field
Embodiments of the present invention relate to an organic light emitting display device, particularly an organic light emitting display device operating in a concurrent (or simultaneous) emission method.
2. Discussion of Related Art
Recently, a variety of flat panel displays that reduce disadvantages of cathode ray tubes, such as weight and volume, have been developed. Typical flat panel displays include liquid crystal displays, field emission displays, plasma display panels, organic light emitting display devices, etc.
An organic light emitting display device is a flat display device that displays an image using organic light emitting diodes that emit light by the recombination of electrodes and holes and has high response speed and low power consumption.
In general, organic light emitting display devices are classified into passive matrix organic light emitting display devices (PMOLED) or active matrix organic light emitting display devices (AMOLED), in accordance with the methods of driving the organic light emitting diodes.
An active matrix organic light emitting display device includes a plurality of scan lines, a plurality of data lines, a plurality of power source lines, and a plurality of pixels coupled with the lines and arranged in a matrix. The pixel includes an organic light emitting diode, a driving transistor for controlling the amount of current supplied to the organic light emitting diode, a switching transistor for transmitting a data signal to the driving transistor, and a storage capacitor for maintaining voltage of the data signal.
The active matrix organic light emitting display device has low power consumption, but may have a display that is not uniform because the magnitude of a current flowing through an organic light emitting element may vary due to variations in a voltage difference between the gate and the drain (or the gate and the source) of a driving transistor that drives the organic light emitting element, that is, a threshold voltage (or a threshold voltage difference) of the driving transistor.
That is, properties of the transistors disposed in the pixels are changed by variables in the manufacturing process, and accordingly, the threshold voltages of the driving transistors vary between the pixels. Therefore, a compensating circuit that can compensate the threshold voltage of the driving transistors may be additionally formed to remove the non-uniformity between the pixels.
The compensating circuit, however, additionally includes a plurality of transistors and capacitors, and signal lines controlling these transistors. Therefore, the pixel including the compensating circuit has a problem in that the aperture ratio decreases and the possibility of defect increases.